


an unexpected time

by KantexWolf



Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap, Eventual Relationships, Eventual Smut, Fontcest, M/M, Mating Cycles/In Heat, Monster Heat, Skeleheat, Underswap Papyrus, Underswap Papyrus/Sans, Underswap Sans, jerking off
Language: English
Status: In-Progress
Published: 2016-11-15
Updated: 2017-03-29
Packaged: 2018-08-31 04:34:32
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 2,064
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8564251
Author URL: https://archiveofourown.org/users/KantexWolf/pseuds/KantexWolf
Summary: Sans has to learn the hard way what happens every month, via bro. (A.k.a heat)





	1. Chapter 1

**Author's Note:**

> I update REALLY SLOWLY and dont really do so unless it gets a bit of attention

Soft light rays of sunlight flitter though the old blinds of a timber house, lightning the colourful room inside with a comfortable warmth. In this particular room, clad with bright purple and blue carpet, a small figure shifts in a cosy plane shaped bed. This small figure was in fact a small skeleton, only 4 feet tall and dressed in his ‘battle body’ his shiny blue armour, his most prized possession.  
Rarely does he ever disrobe himself of the suit. The little skeleton stirs in his sleep, turning to face the window. His eyes open and immediately shut again at the intrusive light, with a bit of a groan he opens his eyes slowly to the light and blinks his eyes to adjust. His mouth turns upwards, appreciating the slow wake up and enjoying feeling his body come too. Although excitement and lots of yelling come first nature to him doesn't mean he doesn’t like certain lazy tendencies. Sleep was important after all.  
Right enough lazing about, time to start the day! The little skeleton bounds from his bed, feet hitting the colourful mat and blanket thrown across the room. He stretches he hands above and feels pleasant cracks rattling through his body.  
He excitedly bursts out into the hall way, door slamming upon exit and races down the stairs. He races through the lounge room and takes a sharp turn into the kitchen, exuberance clearly shown with stars in his eyes. He grabs out his favourite pots and pans, loud clanking with his movements in complete contrast to his soft humming. As soon as he puts the cooking utensils down those few seconds before he races of to do the next thing, he hears a soft click of the washing machine in the neighbouring room.  
That’s odd. He didn’t put on any laundry?  
The only other person in the house is his lazy brother, papyrus. Wait, surely his older bro, the one that never cleans anything could be....doing something!? In this new situation he quietly sneaks around the corner, peering in slightly to see. Oddly enough, guess who it is.  
Papyrus.  
He's standing there, a half full basket of dirty beddings next to him, the machine whirling way with the other half. He seems a little off though orange lightly dusting his cheeks and his usual slouched relaxed posture a little more stiff than normal. He hasn’t even thrown on signature orange hoodie he dressed in his PJs, something sans hasn’t seen him wear in a very long time. Although they seem to fit his frame a lot closer than his everyday baggy attire, sans notices as he looks at his brother his face has warmed, blue crossing his face. Sans shakes his head willing the blush to go away, when a low, husky voice inflicted by sleep, speaks up nervously.  
“a-ah, sans what are you..? Isn’t it s-still e-early?”  
Sans slowly steps out from around the Corner, looking and feeling a little guilty about spying on his brother. He replies in kind his voice small and child-like.  
“no, not really...I mean it’s even a little later than I normally wake up, I laid in this morning....?”  
Papyrus almost sobers instantly, surprise lighting his face. A shit eating grin replacing the surprise immediately. Dread falls upon Sans's face in recollection, oh no, he just admitted..!!  
“I’m shocked! the amazing sans, my energetic little sansy being... *gasp*.. LAZY!?”  
Sans retorts immediately, setting into his nagging tone.  
“I am NOT being LAZY and I will never be as lazy as you are!!”  
Papyurs smirks again looking down at his basket full of washing and back up to sans, communicating, without speaking. ‘I'm not the one being lazy here.’  
Sans realizing this struggles to come up with a comeback, spluttering away and now also beginning to flush madly. He stops half way though a garbled sentence when a sent wafts into his nasal passage. It’s sweet and citrusy with a hint of bitter mixed in, making a musky, filling smell. It really quite nice.  
Really nice.


	2. the smell

Was papyrus wearing it? Is it a perfume? Where did he get it from?

Questions poured into Sans’s mind and confusion and intense thinking must’ve shown on his face as pap goes back into a stiff and uncomfortable stance. 

“S-Sans what are you doing there, buddy?”

Papyrus calls out to sans, nervous and perhaps even fearful. Sans snaps back into reality not recalling not even being gone. Sans responds while still deciphering, making it seem as though sans wasn’t all there.

“Hmm?....nothing, just. Trying to figure this smell.....”

Sans decides that following the smell might help find the source of it. Sans slinks unknowingly towards papyrus, his eyes closed to get a bead in on the smell. Papyrus stiffens like a plank and immediately tries swaying his little brothers curiosity.

“S-SANS! YOu, your, um uummmmmmmheeyy??”

Sans is now right in front of papyrus, face-to-face and sans opens his eyes at pap’s awkward ‘hey’ getting surprised and jumping back a bit upon realising how close he was. Even so Sans inches back in slowly Interested on why his nose led him to his bro.  
Papyrus is almost panicking, sweating and shivering, sans is so close maybe he could....no! No, he cant do that!

Sans takes in the fact that pap looks very awkward, he’s flushed and completely avoiding eye contact, sweating and practically shivering. The smell, the smell just gets stronger. Gosh! Why is this musk so alluring, so sweet, so filling...  
Sans’s clear thinking has been thrown out the window in favour of getting more of that delicious, succulent smell leans closer to papyrus, his mouth centimetres away. Papyrus lets out a small shuttered breath, and sans....moves away.

Although papyrus’s breath smells citrusy its not the source, sans moves down pap’s jawline. Papyrus letting out little breaths, not expecting that sans, his small innocence, little brother, sans is the one to act like this.  
sans suddenly stops, and takes a couple of deep inhales at papyrus’s neck. The smell was so strong it was intoxicating, it was so good.  
He had to have a taste.

Sans slowly moves in looking at what he could see of papyrus face, looking for disgust or anything towards moving away. In fact papyrus tilts his head away allowing more access, sans chuckles low and quiet at his brothers actions. His big brother always knew what was his mind. So cool.  
Papyrus trembles a little in nervousness and excitement. Papyrus knows how he likes sans is wrong, but like this he didn’t have to feel guilty. Just let his little bro do what he wants and take what he wants. He can explain later about heats and what the smells do to monsters around them. Even though keeping such information to himself is making him feel more and more guilty, as the seconds tic by the bated breath of his brother hits his neck and the guilt Steadily moves to anticipation.

Sans, admittedly a little scared just runs his tounge along papyrus neck. Then pulls away a little, nervous and trying to fight the haze in his mind.  
Sans breath cools the saliva on Papyrus’s neck, making him shiver. Papyrus softly loops his arms around Sans’s neck and hopes he’ll get the hint to keep going, luckily sans on instinct wraps his own arms around papyrus. Although because of the difference in their heights sans wraps his hands around papyrus lower spine resting on his hips, bumping a sensitive spot for the older sibling.  
“hah!...mm”

Hearing the gasp of his older brother made sans snap out of what he was doing, the fog lifted from his mind. What the hell WAS he DOING!?  
Flinched out of his brothers arms immediately recoiling in on himself, he was just, just.....feeling up his brother! His eyes quickly flicker back into vision, the shock before turning him momentarily blind. He looks at his brothers face, a thousand different outcomes flicking though his mind but the most prevalent is fear and disgust. That most definitely wasn’t the case though as papyrus was flushing a bright orange and a concerned look on his face, jaded by that of...lust.  
Sans felt disgusting, he wanted to throw-up! This couldn’t be real he just did all of that, forced himself on his brother....

Sans stumbles back wanting to flee the situation, but to his absolute horror as he stepped back he felt the rubbing of his pants against a very predominant protrusion. He doesn’t need to look he just grabs the hem of his shirt and, with fresh tears now streaking down his face apologies profusely. Before he can ruin his relationship anymore between his brother and him, sans runs quickly off to his room; leaving his brother completely confounded, papyrus wasn’t able to get out a word before the almost slamming of the door up stairs. 

Papyrus fucked up, he fucked up big time the guilty feeling he had pushed to the side lines swerving back in with a vengeance. Now with self-hate and anger at himself being the whip-cream on top. He should of told sans, should of told him what the smell of...... “heat” does to others!

"god that was STUPID!"

Papyrus angrily yelled to himself in his mind.

‘I shouldn’t of let that happen! I knew what was going on and i goddam let it and fucked things up because of my stupid selfishness!!’  
Papyrus, finally feed up with himself teleported to the middle of the forest where he finally let himself vent.

“DAMMIT, FUCKING, FUCK!”  
Each syllable yelled and profanity said quelled his anger fell till was nothing but a numb feeling welled inside his chest. He supposed he’ll give time for sans to calm down and decide if he hates him yet. deciding even though he’s in his old P.J’s and his heat still simmering below the surface, to go to muffets where he can forget about things for a little bit.

 

Sans stands listless in the middle of his room, wondering how this morning could’ve turned out so bad. He rolls though his head what happened, how everything seemed to go by in a blur; faded from reality. Sans wasn’t away in his mind for long when a painful throb brings him back to the present, sans feels surprised and disgusted that hes still “turned on” after everything that’s happened. He wants it to go away to not deal with this while this emotionally conflicted, but his body has a different idea the erection bordering on painful from the lack of stimulation. Sans sighs dejectedly.

“if I just...g-get it over with...I can just sleep the day away or something...”

Sans, deciding to quickly solve the problem, brings his left hand down to lightly rub over the fabric. “mm-mm” his sensitivity was heightened from leaving his member so long, his legs shaking slightly from the sudden rush of pleasure. Sans stumbles back towards his bed till the back of his legs hit the edge and he falls into it letting himself relax on his bed. Unbidden his right hand slinks under his shirt to rub his lower ribs, a pleased hiss escaping him. He steps it up quickly eager to forget everything, his unoccupied hand drifting down underneath his pants. He sucks in a breath as he starts slowly and firmly jerking his cock, moving his other hand from his lower ribs and moving to his spine to increase the pleasure. Low moans and breathy groans coming from sans uncontrolled, no longer caring for making a ruckus. His moans only increase in volume as he works himself to his blissful end.

“haa..haa o-oh goshhmmm...please..i-I need..please!”

So close..! Sans starts to buck into his own hand thrusting and moaning unbidden, till finally, bliss hits him full force, the pleasure making his mind white out. He can just hear himself almost scream brokenly into his room, jerking himself though it. Till finally his orgasm faded and he whimpers from over sensitivity. He put his hands beside himself and relaxes, the afterglow and satisfaction was clearly written on Sans’s face in a small light smile.

The feeling of comfort and satisfaction suddenly drains when a shuffling sound came from his bedroom door. He turned to see the person he most definitely didn’t want to see.

Papyrus.


End file.
